A technique for detecting bit errors of binary data uses a parity or check bit based on the number of bits in a string or word having value one. The parity bit—as one example of an error detection code—allows to detect errors during a reading or writing operation of a data word. The parity bit is concatenated to the data word. Other techniques use different error handling code for detecting and even correction errors of data words.
In general, the used techniques cause additional error handling code that allows at least the detection of errors and sometimes also the correction of the detected errors. The error handling code in the last case is usually called “error correction code” or “error correcting code” or “Error Checking and Correction”, all abbreviated by ECC. The respective code is concatenated to the corresponding data word or stored separately.
Errors can occur during write operations and during read operations. In the first case data is written over existing data in a memory and the data is not accessible at the intended address in the memory. In the second case the data read from a wrong place is returned as wrong data. If a code covers the writing and reading operation, the writing unit and the reading unit, both, have to use the same error detection technique and enough memory space for handling the respective error detection code must be available.